Super oxide, hydroxyl radical, hydrogen peroxide and singlet oxygen, and reaction products thereof with metals or lipids have been known as active oxygen species in a broad sense. The active oxygen species, however, typically include reductive molecular species having a different number of electrons from that of ground state oxygen, such as super oxide, hydrogen peroxide and hydroxyl radical, and also include singlet oxygen which is an excited molecular species although having the same number of electrons with that of ground state oxygen, and they individually have specific characteristics, which cannot be understood in terms of the active oxygen species, based on difference in their electron states. Electron spin resonance (ESR) is widely used for detecting the active oxygen species (Example 9 of Japanese Laid-Open Patent Publication “Tokkai” No. 2001-10954, etc., for example). ESR is effective for detecting radical species such as super oxide, hydroxyl radical and the like, but cannot detect singlet oxygen other than radical species. Singlet oxygen in water has a lifetime of as short as approximately 4 microseconds, so that there is only a limited range of detection methods excellent both in sensitivity and specificity (Japanese Laid-Open Patent Publication “Tokkaihei” No. 7-159325, etc. for example). It is therefore supposed that most of reactions ever reported as involving the active oxygen species in a broad sense, and most of agents ever reported as being effective for trapping the active oxygen species are unexplicit with respect to singlet oxygen, if the detection methods are considered.
In recent years, it has been becoming clear, from researches on the reactivity of the individual active oxygen species, that they show specific reactivity respectively to their target molecules. For example, super oxide and hydroxyl radical readily react with proteins to fragment them. On the other hand, singlet oxygen shows a specific reactivity completely different from that of super oxide and the like, such as forming cross-linkage in proteins to thereby polymerize the proteins (J. Soc. Cosmet. Chem. Japan., Vol.28, No.2, 1994, p.163-171, for example). It has also been made clear that, when healthy skin is exposed to ultraviolet irradiation, singlet oxygens are generated in the skin surface, and causes lipid peroxidation of sebum, which is one of factors for various skin troubles (J. Jpn. Cosmet. Sci. Soc., vol.19, No. 1, 1995, p.1-6, for example). Under such circumferences, contribution of singlet oxygen has been regarded as significant even for diseases and ageing which have conventionally been believed as a result of contribution of active oxygen species. Any agent capable of quenching singlet oxygen may therefore be effective for preventing these diseases and ageing. Most of those conventionally known as the singlet oxygen quenchers, however, tend to degrade during storage due to poor chemical stability of the substances per se, and to lower the ability of quenching singlet oxygen, so that they are in need of further improvement in terms of sustainability of the effect.